24 
BETULACEAE, 
. Lateral buds ellipsoid or oblong, very blunt, small. 2. 
Buds ovoid or fusiform-oblong, acute, at most ciliate. 8. 
. Buds very small (3 or exceptionally 4 mm.). 3. 
Buds moderate for the group (4 mm.): bark papery. 5. 
Buds large for the group (5 mm.): bark papery. 7. 
. Twigs not resinous warty, softly hairy. B. pumila. 
Twigs with resinous warts. 4. 
. Twigs and buds with soft hairs. B. pumila glandulifera. 
Twigs and buds only velvety. (1). B. glandulosa. 
. Buds hairy: twigs warty: bark orange. (2). B. nigra. 
Bud-seales at most ciliate: bark creamy or white. 6. 
. Twigs very resinous-warty: glabrous. (3). B. populifolia. 
Twigs sometimes with long hairs. (4). B. papyrifera. 
. Buds glabrous: bark creamy or white. B. papyrifera. 
Buds hairy: lower scales long: bark orange. B. nigra. 
. Buds acutely ovoid. 9. 
Buds subfusiform, acute, with short lower scale. 12. 
. Twigs puberulent, somewhat warty. B. kenaica. 
Twigs glabrate. 10. 
. Twigs resinous-warty: buds small (3X5 mm.). B. utilis. 
Twigs little warty: buds larger (4-56-8 mm.). 11. 
. Twigs and buds red-brown. (5). B. Maximowiczii. ' 
Twigs and buds brown. B. grossa. 
. Buds short for the group (5-6 mm.). 13. 
Buds long (7-8 mm.): twigs scarcely warty. 17. 
. Twigs softly hairy. 14. 
Twigs glabrous. 15. 
. Pubescence persistent. (6). B. pubescens. 
Pubescent only in sheltered places. B. papyrifera. 
. Twigs very warty and varnished. B. occidentalis. 
Twigs sparingly if at all resinous-warty. 16. 
. Bark white: trees usually weeping. (7). B. pendula. 
Bark yellowish or silvery-gray. (Yellow birch).  B. lutea. 
. Buds light brown: branches red-brown, spicy. (8). B. lenta. 
Buds glossy red-brown. B. japonica. 
